前几天项目中让扫描出所有使用Restful API的方法。刚开始还想着用python过滤关键字来查找的，后来想想可以使用反射来搞的。主要包含以下三个步骤：

1. 根据包名解析包的具体路径
2. 查找指定包下指定注解的类
3. 在上一步骤中得到的类中，依次扫描包含指定注解的方法

想着写着工具类的形式，代码结构如下：

public class AnnotationScannerUtils {private static final Logger logger = LoggerFactory.getLogger(AnnotationScannerUtils.class);private static final String EXT = "class/*** 根据包名获取包的URL* @param pkgName com.demo.controller* @return*/public static String getPkgPath(String pkgName){String pkgDirName = pkgName.replace('.', File.separatorChar);URL url = Thread.currentThread().getContextClassLoader().getResource(pkgDirName);return url == null ? null : url.getFile();}/*** 获取指定包下所有类对象的集合* @param pkgName 包名(com.demo.controller)* @param pkgPath 包路径(/Users/xxx/workspace/java/project/out/production/classes/com/demo/controller)* @param recursive 是否递归遍历子目录* @return 类集合*/public static Set<Class<?>> scanClasses(String pkgName, String pkgPath, final boolean recursive){Set<Class<?>> classesSet = new HashSet<>();Collection<File> allClassFile = getAllClassFile(pkgPath, recursive);for (File curFile : allClassFile){try {classesSet.add(getClassObj(curFile, pkgPath, pkgName));} catch (ClassNotFoundException e) {logger.error("load class fail", e);}}return classesSet;}/*** 获取指定包下包含指定注解的所有类对象的集合* @param pkgName 包名(com.demo.controller)* @param pkgPath 包路径(/Users/xxx/workspace/java/project/out/production/classes/com/demo/controller)* @param recursive 是否递归遍历子目录* @param targetAnnotations 指定注解* @return 以注解和对应类集合构成的键值对*/public static Map<Class<? extends Annotation>, Set<Class<?>>> scanClassesByAnnotations(String pkgName, String pkgPath, final boolean recursive, List<Class<? extends Annotation>> targetAnnotations){Map<Class<? extends Annotation>, Set<Class<?>>> resultMap = new HashMap<>(16);Collection<File> allClassFile = getAllClassFile(pkgPath, recursive);for (File curFile : allClassFile){try {Class<?> curClass = getClassObj(curFile, pkgPath, pkgName);for (Class<? extends Annotation> annotation : targetAnnotations){if (curClass.isAnnotationPresent(annotation)){if (!resultMap.containsKey(annotation)){resultMap.put(annotation, new HashSet<Class<?>>());}resultMap.get(annotation).add(curClass);}}} catch (ClassNotFoundException e) {logger.error("load class fail", e);}}return resultMap;}/*** 加载类* @param file* @param pkgPath* @param pkgName* @return* @throws ClassNotFoundException*/private static Class<?> getClassObj(File file, String pkgPath, String pkgName) throws ClassNotFoundException{// 考虑class文件在子目录中的情况String absPath = file.getAbsolutePath().substring(0, file.getAbsolutePath().length() - EXT.length() - 1);String className = absPath.substring(pkgPath.length()).replace(File.separatorChar, '.');className = className.startsWith(".") ? pkgName + className : pkgName + "." + className;return Thread.currentThread().getContextClassLoader().loadClass(className);}/*** 遍历指定目录下所有扩展名为class的文件* @param pkgPath 包目录* @param recursive 是否递归遍历子目录* @return*/private static Collection<File> getAllClassFile(String pkgPath, boolean recursive){File fPkgDir = new File(pkgPath);if (!(fPkgDir.exists() && fPkgDir.isDirectory())){logger.error("the directory to package is empty: {}", pkgPath);return null;}return FileUtils.listFiles(fPkgDir, new String[]{EXT}, recursive);}/*** 查找指定注解的Method* @param classes 查找范围* @param targetAnnotations 指定的注解* @return 以注解和对应Method类集合构成的键值对*/public static Map<Class<? extends Annotation>, Set<Method>> scanMethodsByAnnotations(Set<Class<?>> classes,List<Class<? extends Annotation>> targetAnnotations){Map<Class<? extends Annotation>, Set<Method>> resultMap = new HashMap<>(16);for (Class<?> cls : classes){Method[] methods = cls.getMethods();for (Class<? extends Annotation> annotation : targetAnnotations){for (Method method : methods){if (method.isAnnotationPresent(annotation)){if (!resultMap.containsKey(annotation)){resultMap.put(annotation, new HashSet<Method>());}resultMap.get(annotation).add(method);}}}}return resultMap;}
}
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具体使用时，可根据具体情况在原方法上二次开发。如果是直接调用，可以实现扫描包含指定注解的类和方法：

    public static void main(String[] args) {String pkgName = "com.demo.controller";String pkgPath = getPkgPath(pkgName);logger.info("pkgPath is {}", pkgName);// 查找包含RestController和Controller注解的类Map<Class<? extends Annotation>, Set<Class<?>>> classesMap = scanClassesByAnnotations(pkgName, pkgPath, true,Arrays.asList(RestController.class, Controller.class));if (classesMap.size() == 0){logger.error("Not exists any class in {} with the specified annotation", pkgPath);return;}Set<Class<?>> classSet = new HashSet<>();classesMap.forEach((k, v) -> {logger.info("get {} classes with {}", v.size(), k.getSimpleName());classSet.addAll(v);});// 查找包含GetMapping和PostMapping注解的MethodMap<Class<? extends Annotation>, Set<Method>> methodMap = scanMethodsByAnnotations(classSet, Arrays.asList(GetMapping.class, PostMapping.class));if (methodMap.size() == 0){logger.error("Not exists any method with the specified annotation");return;}methodMap.forEach((k, v) -> {StringBuilder sb = new StringBuilder();v.forEach(method -> sb.append(method.getName()+", "));logger.info(k.getSimpleName() + ": " + sb.toString());});}--------------------------output-------------------------
01-20 15:06:02.293 [ INFO] [            m.i.u.AnnotationScannerUtils: 29] - pkgPath is com.demo.controller
01-20 15:06:02.363 [ INFO] [            m.i.u.AnnotationScannerUtils: 41] - get 5 classes with RestController
01-20 15:06:02.374 [ INFO] [            m.i.u.AnnotationScannerUtils: 41] - get 2 classes with Controller
01-20 15:06:02.388 [ INFO] [            m.i.u.AnnotationScannerUtils: 55] - PostMapping: login, addFavorite, addUser, logout,
01-20 15:06:02.388 [ INFO] [            m.i.u.AnnotationScannerUtils: 55] - GetMapping: webSiteInfo, info, getCategories, favoritesList, getReportByCityId, queryUserById, getReportByCityName, queryBookById,
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